Semiconductor devices generate heat during their operation, and this heat usually acts to degrade the operation of the semiconductor device. For power semiconductor devices it is necessary to be cooled during operation to maintain acceptable device performance, and for high power semiconductors liquid cooling is often applied.
U.S. Pat. No. 5,841,634 discloses a liquid-cooled semiconductor device. The semiconductors are here placed inside a housing on a plate which is to be cooled. The device shows a fluid inlet port and a fluid outlet port, and a baffle placed in a chamber inside the housing. The baffle includes a wall separating the chamber into a top portion and a bottom portion, and walls separating each portion into compartments. A number of holes in the wall between top and bottom portion provide fluid communication between the portions. Fluid is led from the inlet port to a first bottom compartment, and then through holes to a first top compartment holes to a second bottom compartment. From the second bottom compartment the fluid is led to a second top compartment, where it cools another area of the plate to be cooled. After having passed three top compartments the fluid it led to the fluid outlet port, and out of the device. Thus the cooling compartments of the device are connected in a serial manner.
As the fluid passes the first top compartment, it takes up heat from the plate to be cooled and thus leaves the first top compartment at a higher outlet temperature than the inlet temperature. When the fluid then reaches the second top compartment, additional heating of the fluid will take place, and this will lead to a temperature difference on the cooled plate, from fluid inlet port end to fluid outlet port end. This is detrimental to the lifetime of such a power semiconductor device as high power semiconductors are very sensitive to temperature variations and also sensitive to the general temperature level.
Also the serial connection of multiple cooling compartments will have a high flow resistance as a result, leading to a high pressure drop or a low flow rate of the fluid through the cooling device.